GGShield should validate inputs before passing them to Python Requests

[Sayrus]

GitGuardian Shield Version

• I can reproduce this bug in the latest version

Command executed

• ggshield scan pre-commit
• ggshield quota
• Any ggshield command that uses Python Request

Describe the bug

GGShield uses environment variables but do not validate that the charset used can translate to latin-1 before trying to send a request.
This leads to the following opaque error:

UnicodeEncodeError: 'latin-1' codec can't encode characters in position 6-12: ordinal not in range(256)

For instance, using (Note that these are not ASCII dashes but U+2013 which cannot be encoded using .encode('latin-1')):

GITGUARDIAN_API_KEY=–––––––FILL-ME–––––––––

You get an encoding error.

Expected behavior

When using forbidden characters, a clear error should be provided to the end user. In the example above, this could be:

• Invalid API Key (to match the response that would have been returned by the server)
• GITGUARDIAN_API_KEY must only contains characters that can be encoded in latin-1
• ...

Screenshots

N/A

Traceback (if available)

Traceback (most recent call last):
  File "/home/mraguin/.local/bin/ggshield", line 8, in <module>
    sys.exit(cli_wrapper())
  File "/home/mraguin/.local/lib/python3.8/site-packages/ggshield/cmd.py", line 165, in cli_wrapper
    return_code = cli.main(standalone_mode=standalone_mode)
  File "/usr/lib/python3/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/mraguin/.local/lib/python3.8/site-packages/ggshield/quota.py", line 18, in quota
    response: Union[Detail, QuotaResponse] = client.quota_overview()
  File "/home/mraguin/.local/lib/python3.8/site-packages/pygitguardian/client.py", line 307, in quota_overview
    resp = self.get(
  File "/home/mraguin/.local/lib/python3.8/site-packages/pygitguardian/client.py", line 177, in get
    return self.request(
  File "/home/mraguin/.local/lib/python3.8/site-packages/pygitguardian/client.py", line 129, in request
    response: Response = self.session.request(
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 439, in send
    resp = conn.urlopen(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 387, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/lib/python3.8/http/client.py", line 1252, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1293, in _send_request
    self.putheader(hdr, value)
  File "/usr/lib/python3.8/http/client.py", line 1225, in putheader
    values[i] = one_value.encode('latin-1')